package day10;

import java.util.Scanner;

public class demo3 {
    public static void main(String[] args) {
        Scanner in=new Scanner(System.in);
        int n= in.nextInt(),m= in.nextInt(),x= in.nextInt()+1,y= in.nextInt()+1;
        int [][]dp=new int[n+2][m+2];
        dp[0][1]=1;
        for (int i = 1; i <=n+1 ; i++) {
            for (int j = 1; j <=m+1 ; j++) {
                int t=Math.abs(x-i)+Math.abs(y-j);
                if (t==3||(i==x&&y==j)){
                    dp[i][j]=0;
                }else {
                    dp[i][j]=dp[i-1][j]+dp[i][j-1];
                }
            }
        }
        System.out.println(dp[n+1][m+1]);
    }
}
